Field of the Invention
It is the common practice to provide compressor air for the purpose of cooling a multiplicity of turbine machinery parts. Thus, it is know to provide compressor air to shrouds, which in situ, surround a stage of turbine blades, and thereby form an outer wall of an associated turbine annulus in which in operation, the stage of blades rotates.
A first drawback to the know system is that it necessitates the provision of duel airflows, one for cooling the downstream ends of the shrouds, and another for cooling the upstream ends thereof. This results in the use of a quantity of air which consequently cannot be used for combustion, and further results in a noticeable drop in engine efficiency.
A second drawback in known structures is that the air used for cooling the upstream ends of the shrouds, by virtue of structure, could not be finally ejected into the gas stream in the annulus, without disturbing the flow. This added further to efficiency losses.